(CNN) -- A NASA review released Wednesday found no evidence that astronauts flew aircraft or spacecraft while under the influence of alcohol.

NASA found no evidence to back up claims that intoxicated astronauts have been allowed to fly.

The agency carried out the review after anecdotal evidence emerged of astronauts flying while intoxicated.

The report, written by Bryan O'Connor, chief of NASA's Office of Safety and Mission Assurance and himself a former astronaut, was posted on the agency's Web site.

"Within the scope and limitations of this review, I was unable to verify any case in which an astronaut spaceflight crewmember was impaired on launch day, or any case where a manager of a flight surgeon or co-crewmember disregarded their recommendation that a crewmember not fly shuttle or Soyuz," O'Connor wrote.

The review was ordered in July after an independent panel commissioned by NASA reported two alleged cases in which astronauts were so intoxicated that flight surgeons or fellow astronauts raised concerns over flight safety. The astronauts in question were allowed to fly, the panel said.

The committee was convened by NASA to look into the agency's medical and psychological screening processes after the February arrest of former astronaut Lisa Nowak for the alleged attempted kidnapping of another astronaut's love interest.

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"Interviews with both flight surgeons and astronauts identified some episodes of heavy use of alcohol by astronauts in the immediate preflight period, which has led to flight safety concerns," the committee's July report said.

"Alcohol is freely used in crew quarters. Two specific instances were described where astronauts had been so intoxicated prior to flight that flight surgeons and/or fellow astronauts raised concerns to local on-scene leadership regarding flight safety. However, the individuals were still permitted to fly."

Because the independent committee had promised its witnesses anonymity, committee members were reluctant to divulge sourcing information to O'Connor.

So, O'Connor interviewed about 90 current and former astronauts, flight surgeons, nurses, technicians, managers and staff of the crew quarters. He also reviewed records of calls to safety hotlines, submissions to the NASA Safety Reporting System and NASA's close call and mishap reporting systems for any evidence pointing to astronaut alcohol abuse.

He found no evidence of inebriated astronauts, the report said. Though individuals were able to file reports anonymously, none did so, he said.

"The lack of privacy on launch day makes it nearly impossible to hide alcohol use or alcohol-induced impairment," O'Connor wrote. "Could a crewmember drink to the point of inebriation in his/her room the night before launch? Certainly, but, from the time the crew wakes on launch morning until they lift off, they are surrounded by other astronauts, managers, support crew, television cameramen, still photographers, crew quarters staff and others."

The review recommends that NASA position a flight surgeon in the suit-up room as astronauts are making their final preparations before departing for the launch pad "to allow more direct contact with the crewmembers on launch day and reduce the reliance on a suit tech (non-clinician) picking up any last-minute medical issue."E-mail to a friend